Moisture content of feed grains is critically important to the quality and palatibility of the finished feed. It also has a significant impact on the ease with which they are processed into feed, but has been a largely uncontrollable variable in the feed manufacturing process. Moisture levels encountered typically range between eight and sixteen percent in stored grain. New crop grain can have moisture levels in excess of twenty percent. A feed manufacturing facility will commonly process several hundreds of tons of feed grains each day that have been purchased from many sources. Within a matter of minutes the moisture content of the grain being processed can vary several percentage points. Without regulated moisture addition, a highly varible feed product is produced.
The processing of feed grains in the manufacturing of finished livestock feeds is intended to increase the feed value of the grains. "Value" is defined in terms of palatibility and digestibility. The most simple processing involves either the grinding or dry rolling of the whole kernel grain to fracture the seed coat and to increase the surface area of the grain particles for more efficient digestion. Grain moisture content greatly affects the texture of the final products produced by these dry methods. Very dry grain will tend to make flour, which the animals will not eat, rather than the desired larger particle. This flour, or dust, represents a safety hazard in the feed mnufacturing facility, both from the explosion potential and from workers breathing it. It also represents a loss of inventory to the feed manufacturer. Careful control of the moisture level of the grain entering these dry processes can eliminate dust and help to produce a uniform particle size that will improve digestion without being so small as to depress consumption. Swine and beef cattle feeds are commonly prepared with dry processed grain.
A more sophisticated method of processing feed grains involves cooking them with steam before they are passed through a roller mill. The cooking partially gelatinizes the starch in the grain, increasing its digestibility. The rolling increases surface area of the grain kernel by pressing it into a flat "flake". Beef and dairy cattle feeds are commonly steam flaked. Whole kernel grain flows through a chamber into which live steam is injected. Once "cooked", it passes through a roller mill, producing a "flake". If the grain is too dry, the cooking or gelatinizing will be incomplete, since the gelatinizing process requires both heat and moisture. The grain kernel will be hard and require more energy to roll than a moist, properly cooked kernel. The final flake will be dry and brittle. Subsequent handling of the flake will cause it to break, resulting in "fines" that the animal will not eat readily.
A second processing method involving steam cooking of the grain is pelleting, which is commonly used to prepare poultry feeds. The grain is ground to a uniform texture, mixed with other feed ingredients and treated with steam. The resulting mash is extruded through a die in a pellet mill. As with steam flaking, gelatinization and toughness of the final feed form, are greatly influenced by the moisture content of the grains being processed. The power required to drive the pellet mill is also affected by the moisture content of the mash. If it is too dry, more power will be required to extrude the pellet, the cooking will be incomplete and the feed ingredients will not bond well, causing a weak pellet that falls apart. Broken pellets become "fines" that are not eaten and represent a loss to the livestock producer.